The invention relates to a signal clamping device and a method thereof and a related optical storage system, and more particularly, to a signal clamping device capable of clamping a signal with a variable clamp level that is set according to a frequency characteristic of the signal, and to a method thereof and a related optical storage system.
It is well known that a conventional optical storage system generally includes a conventional focus servo output (FOO) signal clamping device for clamping an FOO signal which has a level exceeding a predetermined clamp level so as to prevent a focus actuator from moving an objective lens in an optical pick-up head of the optical storage system to hit an optical disc. However, the predetermined clamp level is not adjustable, and thus the conventional FOO signal clamping device will result in an over limit problem.
Please refer to FIG. 1. FIG. 1 shows a bode diagram of a lead compensator in a focus compensator of the conventional optical storage system. As shown in FIG. 1, a high frequency component of a FOO signal generated from the lead compensator will have a higher gain, and thus the high frequency FOO signal may tend to be clamped more easily. The high frequency FOO signal may act as accelerating the lens to follow the vibrated disk, not like the low frequency FOO signal which may act as moving lens to a certain position and may hit the optical disk easily. Thus, the FOO signal having a high frequency component sending to the FOO signal clamping device is easily subjected to be improper clamped. Therefore, an efficient and economical solution for preventing the objective lens in the optical pick-up head of the optical storage system from hitting the optical disc without having the over limit problem is eagerly required at present.